The Stovebolt Site Forums The Shop Area Engine Shop Plastigauge question...

After getting everything together I used Plastigauge to check clearences. Front three bearings were .001-.0015. Rear Main Was .0015 at the rear most part of the bearing but .003 on the font end. Manual says .0005-.0045. Any reason to shim? even .001 to get closer to the middle of the range? Thanks!

That crankshaft journal has a little taper wear. Just live with it- - - -the only way to correct that problem is to regrind the crankshaft to the next undersize, and then search for another set of main bearings. Plastigauge is sort or a SWAG (Scientific Wild-donkey Guess) anyway- - - - -it's better than nothing, but not as accurate as most people think. To get a true oil clearance, the bearing bore and the crankshaft would have to be measured separately before assembly. That's how race engine builders do it.
Jerry

I disagree with the Plastigauge being just a guess. Its plenty accurate for a street driven engine, they been selling it for 60 or more years that I know of. Felpro used to supply it in the overhaul gasket sets. It can't be all that bad if it shows a .0015" taper.

On the rear main with tapered readings, if it has a shim pack, verify they are flat and not causing the taper. You might also pull the rear cap and bearings to verify no trash is under a bearing. .0015" is pretty tight for a main bearing.

Double check the clearance after a good cleaning, then if its still not even, ask your machines about it.

Jerry- It's the same 1955 passanger car block we discussed notching the block for later bearings. I never noticed the cap missing the hole until I tried to put the bearing into the cap, I was quite suprised. I did look at the old bearing and noticed it too waas missing the dowel itself. I feel pretty strongly that this engie was purchased from a rebuilder at some point.

Here are the anomalies I've found so far

It was in a 1954 chevy truck

it's a 55 passanger car block

Has a 1962 head

The baffle for the road draft tube was missing

When I removed the rod/piston assemblies I checked the numbers stamped on the rods and caps when I got to rod 5 it was stamped with a 4, so two number 4's (I did re-mark them for re-assembly) so the numbers were 1, 2, 3, 4, 4, 6

There were 4 different paint colors on the engine- Pan- grey, block and head- black, valve cover- red and draft tube- blue

Then there's the cap with no hole for the dowel and matching bearing

Crank cut 10 on the mains and 20 on the rods

pistons are 60 over

So yeah, the whole thing is a mismatch